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Jack Dennis

In the 1950s, scientists would occasionally create a game as a demonstration, a research aid, or a training exercise, but these programs were usually short on interactivity and not intended primarily for entertainment. Tennis for Two can be considered an exception to this general rule, but even it was quickly dismantled after being played by a few hundred visitors to the Brookhaven National Laboratory. The academic and military-industrial research communities working on their batch processing computers were simply not interested in entertainment. And this attitude was perfectly understandable: with a computer representing a multi-million dollar investment, there was simply no time to waste on frivolous pursuits and no way to create a viable entertainment platform for use by the general public.

But at MIT in the late 1950s, something new was emerging in Building 26: an interactive computing environment accessible by nearly anyone affiliated with the university. The exploits of Kotok, Samson, and friends on the TX-0 birthed a new class of skilled computer users more interested in having fun than in performing actual research. This fun did not generally include games on the TX-0, which was still somewhat limited in speed and display capability, but these hacks laid the groundwork for the more advanced interactive programs to come. When the PDP-1 computer arrived at MIT in 1961, the TX-0 hackers were prepared to take their exploits to the next level. The result was the creation of the first (relatively) widespread and influential computer game, Spacewar!

Every monograph written on the history of the video game from Leonard Herman’s Phoenix to Tristan Donovan’s Replay has at the very least mentioned Spacewar!, and most of them discuss the creation of the game in depth and give it pride of place as the the game that truly launched the computer game phenomenon and influenced some of the earliest commercial products in the field. These accounts are largely drawn from just two sources: Stephen Levy’s book Hackers: Heroes of the Computer Revolution, for which the author interviewed most of the principle players in the MIT hacking scene, and an article Spacewar! co-creator J. Martin “Shag” Graetz wrote for Creative Computing magazine in 1981 entitled “The Origin of Spacewar.” As such, there is little disagreement between the principle sources on the inspiration for and the development of the game. Still, there are a few minor aspects of the narrative that have become muddled over time, which I will point out in my summary below.

Hacking the PDP-1

Some of the key contributors to the TX-0 and PDP-1 hacking scene at a Computer Museum event in 1984.

Even before the PDP-1 had formally arrived at MIT, the TMRC hackers began planning new coding exploits. According to Levy, Kotok learned about the machine’s impending installation while working a summer job at Western Electric in New Jersey and resolved to translate the debugger originally written by Jack Dennis as FLIT and then modified by others to become micro-FLIT to the new computer so that the hackers would have a superior programming environment the moment the PDP-1 came online. Peter Samson gave the new debugger the name DDT (both FLIT and DDT were pesticides, so the names were meant as puns related to “debugging”). As on the TX-0, the hackers wanted to build an improved assembler as well, but Dennis was perfectly happy with the default assembler that had been created by Bolt, Bernake & Newman. Kotok therefore made a deal with Dennis: if the hackers could create a new assembler over a single weekend, Dennis would pay them for their time on behalf of the university. Late one Friday in September, Kotok, Samson, Saunders, Wagner, and two others began frantically coding. By Monday morning, the assembler was done.

Like the assembler and debugger, much of the hacking done on the PDP-1 by TMRC consisted of extensions to existing hacks on the TX-0. One of the more impressive programs came from Samson, who converted his music program to the new machine. The original program on the TX-0 could only play a single voice, but the new program took advantage of the extended audio capabilities of the PDP-1 to create three-part harmonies. This feat of ingenuity so impressed DEC that the company actually made it freely available to its customers. Steve Piner, another TMRC member who matriculated to MIT in 1958, and Peter Deutsch, a precocious local teenager who joined the TX-0 and PDP-1 hacking crowd, developed a text editing program they called “Expensive Typewriter.” Another interesting hack allowed the TMRC members to serially link the PDP-1 and the TX-0 so that inputs made on one computer would also appear on the other. This hack played a role in a practical joke in which the TMRC programmers claimed to have an amazing new chess AI running on the PDP-1. In actuality, the “computer” was a person inputting commands on the attached TX-0. This was apparently the closest the TMRC hackers got to creating an actual game on the computer, as they remained focused on other areas of programming. However, a separate group of computer enthusiasts only tangentially affiliated with TMRC were brainstorming their own ideas on how best to exploit the capabilities of the PDP-1, and they were looking to create a more interactive experience.

ConceivingSpacewar!

Stephen “Slug” Russell, father of Spacewar!

In early 1961, three men in their mid twenties named Wayne Wiitanen, J. Martin Graetz, and Stephen Russell were working in the Littauer Statistical Laboratory at Harvard University, MIT’s close neighbor in Cambridge. According to an interview I conducted with Wiitanen, he and Graetz — called “Shag” due to his propensity for telling shaggy dog stories — became friends as freshmen at MIT in 1953, first meeting through the MIT Outing Club and quickly drawn together by a mutual interest in both rock climbing and playing music. Awarded a scholarship for his freshman year, Wiitanen subsequently lost his financial aid the next year, forcing him to find a new source of income. This led to a part time job at the Datamatic Corporation, the joint Raytheon-Honeywell computer company, in the Spring of 1955, where Wiitanen learned to program for the first time on an IBM 650. The next year, Wiitanen took a work-study job with the MIT Office of Statistic Services. Scheduled to graduate in Spring 1957, Wiitanen never completed a required senior thesis, but his computer experience landed him a job in the MIT Meteorology Department that Summer. After six months of compulsory military training in early 1958, Wiitanen took a job at the MIT Electronics Systems Laboratory before taking the job at Littauer in 1959.

According to Wiitanen, he and Graetz moved into a men’s cooperative called Old Joe Clark’s in the fall of 1957, where Graetz concentrated on various writing projects while Wiitanen worked for MIT. In 1959, Graetz and Wiitanen moved into an apartment at 8 Hingham Street in Cambridge, which they referred to as the “Hingham Institute” — a play on MIT’s common nickname, “The Institute.” It was during this period that Graetz became interested in Wiitanen’s work for the Meteorology Department and began paying attention to computers. According to an interview I conducted with him, Graetz, a native of Omaha, Nebraska, had been a chemistry major at MIT, but harbored no real love for the field and ultimately failed to graduate. After leaving the school, Graetz briefly pursued work as a chemistry lab technician at both his alma mater and Massachusetts General Hospital before Wiitanen arranged for him to be hired by Littauer as a junior operator feeding punched cards into the lab’s IBM 704 computer. He later became a program librarian while also immersing himself in the inner workings of the 704 and learning both assembly language and FORTRAN. According to Wiitanen, Russell was hired by the lab as a program consultant soon after, and the three men shared an office there.

According to Graetz in his Creative Computing article, he, Wiitanen, and Russell spent their idle hours working their way through the Lensman and Skylark novels of E.E. “Doc” Smith and going to local theaters to watch the latest B-movies released by Toho Studios of Japan. Doc Smith was a writer of trashy science fiction novels active in the 1920s and 1930s who laid the foundation for the “space opera” genre with his tales of intergalactic war and romance full of melodramatic dialogue, sudden plot twists, and cliched struggles between good and evil. The Toho movies, meanwhile, featured thin plots, extensive special effects, and numerous explosions as monsters like Godzilla and Rodan terrified Tokyo. Graetz and his friends dreamed of taking the space operas of Smith and adapting them as movies featuring Toho-style special effects.

According to our interview, in summer 1961 Graetz was dismissed from Harvard and called up his friend Jack Dennis, who secured him a job working on a diagnostic program for a new magnetic tape unit for the TX-0 at MIT. When the PDP-1 arrived that fall, he was just as eager as anyone else to begin programming on the machine. He therefore enlisted the Hingham Institute to brainstorm how best to demonstrate the capabilities of the PDP-1 through their own hack. They wanted to create a demo like the Whirlwind bouncing ball or the TX-0 HAX routine that highlighted the computer’s monitor, but they did not feel that either of those programs really demonstrated their respective computers particularly well because they did not tax the computer to its limits or fully engage the user in a pleasurable activity. According to Graetz, it was Wiitanen who finally articulated that action and the need for skilled user input would result in a particularly engaging demo and suggested flying spaceships around the screen as part of a race, contest, exploration, or fight. According to Wiitanen, this seminal moment came over tea at the Hingham Institute one afternoon and was not inspired by anything more particular than a general love of science fiction and a desire to make good use of the PDP-1 computer. Thinking back to their ambitions to create a Skylark movie, Graetz and Russell immediately honed in on the concept of a space conflict. Regrettably, despite coming up with the initial idea, Wiitanen was unable to participate in its implementation. An army reservist, when the Berlin Wall crisis flared in October 1961, Wiitanen was called up to active duty. Responsibility for implementing the demo, which the trio named Spacewar!, therefore fell to Hingham Institute compatriot Steve Russell.

According to an oral history he participated in with the Computer History Museum, Stephen “Slug” Russell was born in Hartford, Connecticut, to a mechanical engineer father and teacher mother. When Stephen was three, the Russell family embarked on a cross-country train excursion to visit his mother’s family in Washington state, which began a life-long fascination with trains. Model railroads soon became an obsession, which led him to become interested in electronics around the age of ten so he could create more elaborate model railroads. Soon after, his father was laid off and moved the family to Washington, where Russell attended high school. During this period, Russell became more deeply immersed in electronics through surplus World War II radio and radar equipment.

Russell beheld his first computer, Howard Aiken’s Harvard Mark I, as a teenager during a trip back east to visit his uncle, Harvard professor George Pierce. A firm believer that everyone should receive a proper education, Pierce later paid Russell’s tuition so he could attend Dartmouth College. While Dartmouth did not have a computer in those days, Russell did work with IBM tabulating equipment. During his senior year, he fell in with Professor John McCarthy, one of the pioneers in the field of artificial intelligence. When McCarthy moved to MIT in 1958, Russell followed to help implement a new programming language called LISP specifically tailored for AI research. Preoccupied by his AI work, Russell never completed a senior thesis at Dartmouth and therefore did not officially graduate. With his passion for trains, Russell joined TMRC in 1960 and became active in the S&P committee. He did not, however, become involved in the TX-0 programming scene, as he was too busy trying to implement LISP on the 704 in the Computation Center. By 1961, Russell was burned out on LISP and took the job at Harvard that led to his involvement with the Hingham Institute.

There is considerable confusion in the secondary video game literature regarding the relationship of Russell, Graetz, and Wiitanen to both MIT and the hackers of TMRC. Replay, for instance, identifies all three as TMRC members, while All Your Base Are Belong to Us describes the game as being written by Steve Russell and “his MIT engineering friends,” Phoenix refers to Russell as a graduate engineering student at MIT, and The Ultimate History of Video Games refers to Russell as “a fairly new Model Railroader who had just transferred from Dartmouth College.” In truth, none of these descriptions are completely accurate. Russell was certainly not a graduate student at MIT, for he is quite clear in his oral history that he never graduated from Dartmouth. He was not an employee at the time he was creating Spacewar! either, as both his oral history and Graetz’s article place him at Harvard in early 1961 after leaving his AI work at MIT. Graetz claims in Creative Computing that Russell did return to MIT in Fall 1961, but in Russell’s own oral history he gives a rundown of this period and appears to indicate he went straight from Harvard to Stanford in 1962 without any other stops in between. This contention is further supported by a 1963 article about computing at Stanford in Datamation that states Russell “worked under McCarthy at MIT and was brought to Stanford from Harvard,” and by a deposition given by John McKenzie in 1975 in which he stated Russell was at Harvard during the period of time he was creating Spacewar! While he was briefly a TMRC member as demonstrated by the organization’s membership roles and comments in his oral history, he explicitly states in his oral history that he did not become involved in the TX-0 hacking scene. Graetz, meanwhile, did work at MIT, but he has never claimed an affiliation with TMRC and his name cannot be found in the organization’s membership roles. Finally, Wiitanen was never at MIT at all, called to active duty before the PDP-1 hacking exploits could even begin. While TMRC was not directly involved in the conception of Spacewar!, however, its members would still play a critical role in moving the program from concept to playable game.

Building Spacewar!

Dan Edwards (l) and Peter Samson playing Spacewar! c. 1962

Despite no longer being an MIT employee, Russell continued to frequent Building 26 at the university and was therefore in a position to both observe and interact with the PDP-1 when it finally arrived. In his own recollection of the genesis of Spacewar! in his oral history, Russell remembers being particularly inspired to create the program by the “Minskytron,” a graphical demo recently created by professor Marvin Minsky in which three dots were generated on the screen that subsequently began to move around and interact with each other. Based on initializing constants entered by the user, these dots could form a variety of patterns from complex geometric shapes to fireworks effects. Russell’s exposure to the Minskytron and his interest in the new DDT debugger inspired him to implement the previously brainstormed Spacewar! hack on the PDP-1. As Graetz remembers, however, Steve did not acquire the name “Slug” for nothing, as he was generally loathe to start a new project if he could come up with a good excuse to put it off. Therefore, while the game concept took shape in the summer and fall, by December Russell had still not done any programming.

At this point, TMRC made its first critical contribution to Spacewar! As he describes the situation in his own Computer History Museum oral history, Alan Kotok practically served as a project manager as the program got off the ground, giving Russell encouragement and supplying him with bits of code taken from various libraries. As recounted by Graetz, Russell, and Levy, the critical moment came when Russell articulated what turned out to be his final excuse: he did not possess the sine-cosine routines required to place and move his ships around the screen. Kotok, by now considered the dean of the TMRC hacking community, enjoyed a good relationship with the engineers at DEC, so he took it upon himself to drive to the company headquarters in Maynard to hunt down the routines himself. When he returned to MIT and plopped them down in front of Russell, the hacker realized he had run out of excuses and set to work.

According to Levy, Russell finally began attacking the program in earnest in December 1961, but this date is almost certainly incorrect, as according to log files produced during the McKenzie deposition, the PDP-1 display was not installed until December 29, 1961, meaning he could not have even seen the Minskytron in action yet by December. Graetz recounts that Russell first succeeded in generating and moving a dot around the screen in January 1962. Initially worried that moving an entire ship would take too much processing power, Russell realized that since the points comprising the spaceship would always remain in the same relative position to each other, he only needed to calculate the angle once per frame and then implement code that rotated the entire grid as necessary. Before long, Russell had designed the two ships, which according to an interview excerpt with Russell in The Ultimate History of Videogames were designed to look like a curvy Buck Rodgers spaceship and a slender Redstone rocket. They soon gained the nicknames “Wedge” and “Needle” respectively.

According to Levy, by February 1962 Russell, with coding help from TMRC member Bob Saunders, had finished the basic program. (Note: In The Ultimate History of Video Games, Kent claims that Russell spent nearly six months creating the first version of the game, but this contradicts the primary sources, which all give the December to February time frame. It is possible Kent is referring to the total time from conception to implementation as opposed to just the time Russell actually spent programming or that he is including the time when additional modifications were made before the program’s public debut in May.) In this initial version, the two ships could accelerate, rotate clockwise, or rotate counterclockwise when the player flipped one of three toggle switches on the PDP-1. Flipping a fourth toggle switch allowed the player to fire torpedoes that would destroy the opposing ship if they made contact. Originally, there was a random chance that the torpedo would be a dud, but Russell changed them to be 100% reliable after negative user feedback. As explained by Russell to Kent, the game required two players due to a lack of computing power to craft an AI opponent.

A drawing of one of the custom control boxes crafted by the TMRC hackers to play Spacewar!

While Russell finished the basic Spacewar! program in February, there were significant modifications made over the next three months. As Levy recounts in Hackers, the TMRC programmers had by this time developed what he termed the “Hacker Ethic,” which was basically a philosophy that access to computers and tools for discovering how the world works should never be restricted and imperfect systems should always be improved by whomever has the ability to do so. This was essentially a transfer of the sensibilities of the TMRC S&P committee, which was full of students who loved taking things apart to see how they functioned and constantly strove to improve the track layout housed in Building 20 with their own inventive solutions. This “Hacker Ethic” would continue to be a driving force behind the evolution of computer technology for decades and still manifests today in the vibrant game modding communities, the continuing development of open source computer programs, and online collaborative projects like Wikipedia. In the case of Spacewar!, the Hacker Ethic insured that other members of the TMRC hacker community approached Russell with their own suggestions to improve the game. While some assume that TMRC members added these additions directly to the program themselves as part of the Hacker Ethic’s call for taking the initiative in improving computer programs, Norbert Landsteiner, who runs one of the most comprehensive Spacewar!webpages on the Internet, has painstakingly deconstructed and analysed the game’s code and concluded that Russell himself continued to serve as the gatekeeper for new features and incorporated them into his code in an orderly fashion.

The earliest modifications to Spacewar! were applied to the backdrop for the game. As Graetz recounts, Russell realized early in development that without any background objects, it was impossible to tell how the two ships were moving relative to each other when they were travelling at slow speeds. Russell solved this problem by including random dots of light on the screen that represented a star field. This inelegant solution did not satisfy Peter Samson, who decided to extract data from the American Ephemeris and Nautical Almanac to recreate the night sky between 22 1/2 ° N and 22 1/2 ° S down to the fifth order of magnitude. Not only was this routine capable of panning across the screen to display most of the best-known constellations in proper relation to each other, but by controlling the number of times the electron beam fired at any particular spot on the screen, Samson was also able to recreate the relative brightness of each star in the night sky. In the tradition of previous hacks on the TX-0, Samson dubbed his routine “Expensive Planetarium.” According to the game code itself as relayed by Landsteiner, Samson completed Expensive Planetarium around March 13, 1962, and Russell incorporated the code into the next formal release of the game, Spacewar! 2B, on April 2, 1962. (Note: In Replay Donovan appears to indicate that there was no background star field before Samson added Expensive Planetarium, but the primary sources agree that Samson’s contribution was replacing random dots with accurate constellations rather than incorporating background stars in the first place.)

A second critical innovation came from Dan Edwards, a graduate student and TMRC member who, like Russell, worked with John McCarthy on LISP. According to Graetz, Edwards was nonplussed by the lack of strategy in the game, which tended to devolve into the players wildly shooting at each other while zipping across the screen. He believed introducing gravity into the game would provide the necessary strategic depth, but Russell felt making the necessary modifications was beyond his abilities. Edwards therefore implemented the gravity himself, adding a sun to the middle of the screen and modelling its effects on the movement of the ships. This addition actually pushed the display beyond its limits and led to flickering, so Edwards looked for other places he could save resources. He quickly discovered that the program examined the ship lookup table to redraw each ship on each frame, a method Russell had initially used — according to his oral history — so that the shape of the ships could be easily changed on the fly. Edwards created a compiler that consulted the tables at the start of each game instead. This freed up the necessary runtime to incorporate the effect of gravity on the spaceships, but not on the torpedoes, which continued to travel in a straight line right through the sun. Russell and company decided these were “photon torpedoes” that were not affected by gravity to provide an in-game explanation for this effect.

The final significant modification to the game, patched in sometime in April or early May, was a hyperspace function developed by Graetz in which the player could flip a toggle switch to have his coordinates randomly scrambled so he would reappear somewhere else on the screen. According to Levy, this was a concept directly borrowed from Doc Smith and his spaceships that could use a “hyper-spatial tube” to enter “Nth space.” The idea, according to Graetz’s article, dated back to the early brainstorming sessions and was designed to introduce a last ditch panic button, but one that was not completely reliable so as not to be overpowered. In the initial version by Graetz, the player could only enter hyperspace three times, and it was possible to land right in the middle of the sun or end up in a similarly compromising position. This made hyperspace something a player would only want to use as a last resort.

Midway through development, the Spacewar! hackers also made an important quality of life change to the hardware itself. Tired of sore elbows and aching backs from hunching over the PDP-1 display flicking toggle switches — not to mention the constant threat of hitting the wrong switch and aborting the game and the visual advantage always held by one player due to the monitor being off to one side of the control panel — Alan Kotok and Bob Saunders decided to rectify the situation by creating their own custom control devices. According to Graetz, their first preference was for a joystick, but in 1962 the technology was still not common and proved to be unavailable to the hackers. Instead, the duo scrounged around the TMRC rooms for random bits of wood, wire, bakelite, and switching equipment and fashioned them into control boxes. The final result consisted of two levers and a button mounted in a wooden case with a bakelite top. One lever controlled rotation (pushing the lever to the left rotated the ship counterclockwise while pushing it to the right rotated the ship clockwise), the other lever controlled acceleration and hyperspace (pulling the lever towards the player accelerated the ship while pushing it away from the player activated hyperspace), and pressing the button fired torpedoes. With these control boxes, installed according to logs provided during the McKenzie deposition on March 19, 1962, both players could sit comfortably in front of the screen while also becoming more adept players due to the more logical control layout. Essentially, Kotok and Samson invented the first gamepads, an indispensable part of every video game system to come.

Spreading Spacewar!

A black-and-white screenshot of Spacewar! showing the two ships in their opening positions

In May, 1962, Spacewar! made its public debut at the annual MIT Science Open House. According to Graetz, the game was modified for that occasion to incorporate a scoring system to better limit individual sessions, while a larger CRT was also hooked up to the computer to facilitate spectator viewing of matches. Development on the game stalled over the next few months — possibly because Steve Russell was in the middle of a six month stint in the United States Army that he briefly discusses in his oral history — before what could be considered the “final” version of the original game was promulgated by Russell on September 24, 1962. Referred to as Spacewar! 3.1, this version incorporated certain functions that had previously been patched in like the scoring mechanic and hyperspace into the core game logic alongside several minor tweaks.

The same month Spacewar! made its public debut at MIT, Graetz presented a paper to the newly formed Digital Equipment Computer Users’ Society (DECUS), a support group for businesses and organizations using DEC computers that both conducted technical conferences and facilitated the exchange of software between members via magnetic tape, outlining the basic parameters of the game. From there, Spacewar! began to spread across the country. How quickly this spread occurred has recently been the subject of some debate. The traditional narrative, borrowed from Graetz’s article, posits a fairly rapid and widespread adoption of the game. In truth, more recent in-depth research by historians Marty Goldberg and Devin Monnens indicates that the game spread in fits and starts and did not really hit its stride until the late 1960s and early 1970s, when CRT terminals began to supplant teletypes as the primary user input. Nevertheless, it is fair to say that in an era when most game programs were one-offs that remained confined to a specific system, or at the very least a particular geographic area, Spacewar! penetrated computer labs from Cambridge to California, inspiring would-be programmers to follow the hacker ethic by creating their own variations on the game or even creating their own original programs. This activity culminated in the early 1970s in the creation of the first arcade video games — which were directly inspired by Spacewar! — and the subsequent launch of a new video game industry.

The main hubs of Spacewar! activity appear to have primarily formed around MIT hackers who brought the game directly to other institutions. The most important of these hubs was undoubtedly Stanford University, where Steve Russell ended up working in 1962 when he followed John McCarthy to the institution, who had grown frustrated with the lack of progress in AI research at MIT therefore decided to continue his work at Stanford. Spacewar! made the trip to the West Coast with Russell and became an immediate smash success, with a 1963 article in Datamation reporting that system administrators at Stanford had banned playing the game during business hours because its overwhelming popularity placed too much strain on system resources. Every time McCarthy’s research team received a more advanced computer, it received a Spacewar! port, keeping the game relevant among the computer-using crowd at the university for at least a decade. Indeed, in October 1972 Stanford became the site of what may have been the first organized video game tournament, the “Intergalactic Spacewar Olympics.” This event was famously chronicled by Stewart Brand for the December 1972 issue of Rolling Stone Magazine, giving Spacewar! a cultural cachet rare for computer games of the period. Furthermore, it was through Stanford that Bill Pitts and Nolan Bushnell, the originators of the first two arcade video games, were both first exposed to the landmark program that directly inspired their creations. (Note: I am aware that Mr. Bushnell claims to have first seen Spacewar! at the University of Utah, but that is a story for another blog post.)

Perhaps the best documented Spacewar! hub after MIT and Stanford is the University of Minnesota, where an MIT alum named Albert Kuhfeld programmed the game on a CDC 3100 computer in the Department of Physics and Astronomy that was being used in tandem with a new particle accelerator. According to interviews conducted by Landsteiner for his website and Goldberg and Monnens for their paper, Kuhfeld began programming the game soon after the computer arrived in 1966 because he missed his Spacewar!-playing days at MIT, but he was not able to do much actual programming until 1967. By 1969, the game was essentially complete. According to Goldberg and Monnens, the main differences between “Minnesota Spacewar” and the MIT version were the inclusion of timers for torpedoes, retro rockets for deceleration, and the “Minnesota Panic Button,” which activated a cloaking device. According to Landsteiner, Kuhfeld took a cue from MIT and fashioned control boxes for his version as well, with one lever for left/right, one lever for acceleration/deceleration, a button for torpedoes, and a switch for hyperspace/invisibility. A second control box replaced the movement buttons with a joystick. According to Goldberg and Monnens, Kuhfeld’s game normally had to be played during the day rather than at night, when the accelerator was often running, and could therefore only be played rarely at first. Eventually, more computer hardware was added to the lab, allowing playing time to increase and the game to become more popular. In July 1971, science fiction magazine Analog published an article about the game submitted by Kuhfeld himself, which, like the Rolling Stone article by Brand, helped raise Spacewar!‘s national profile.

Beyond MIT, Stanford, and Minnesota, evidence of Spacewar! distribution and popularity becomes increasingly sketchy and anecdotal. According to Goldberg and Monnens, the game spread quickly to other Boston-area institutions with PDP-1 computers and migrated to at least a few institutions farther afield like the University of Michigan, where the game arrived sometime between 1964 and 1966. This spread was at least partially aided by DEC itself. Because the game had been created specifically to use every last ounce of processing power the PDP-1 could bring to bear, DEC recognized that the program was a perfect poster child for the capabilities of the system. In 1963, DEC created a promotional brochure for the PDP-1 based around Spacewar! that highlighted the impressive number of calculations per second the computer performed to run the game as well as the complexity inherent in plotting the position of the ships and stars and modelling the Newtonian physics present in the game.

According to most sources, DEC further helped the spread of Spacewar! by eventually including it as a test program with every PDP-1 computer sold. The claim, as related by Levy and parroted by numerous sources thereafter, is that because the program used virtually every function of the PDP-1, it was a perfect final diagnostic program for the engineers at DEC before shipping a computer to the end user. Because the computer was then shipped without the memory being wiped, the game would run the first time the computer was turned on at its final destination, exposing yet another computer lab to the game. While this claim makes for a good story, however, it has yet to be confirmed by DEC primary sources. The best we have is the brochure already referenced above, which does prove that at the very least DEC ran demos of the game for potential buyers, and a statement by DEC engineer Gordon Bell to Goldberg that the story sounds plausible, but that he cannot confirm it. Martin Graetz also stated this claim in a 2007 Gamasutra article, but by that point the story had become so widespread that he may not have been speaking from first-hand knowledge. Indeed, his 1981 Creative Computing article is silent on this issue. Even if this story is true, Goldberg and Monnens caution that of the 55 PDP-1 computers sold, only about twenty were ever equipped with a display, and not all of these were equipped with one right out of the box. Therefore, even if this story is true, this method of distribution probably had a relatively limited impact, especially considering that the most important hub at Stanford was not established in this manner.

As the Datamation and Rolling Stone articles cited above demonstrate, Spacewar! became immensely popular on the Stanford campus, inspiring marathon playing sessions and intense competition among players. Goldberg and Monnens indicate, however, that response may have been more muted at other institutions. While the duo have only limited anecdotal evidence at their disposal, discussions with former players at both Harvard and the University of Michigan indicate that only a few people at either institution showed any interest in the game in the late 1960s. Still, the vibrant playing communities at MIT and Stanford coupled with slow yet steady migration to other computer labs across the country still make Spacewar! the first landmark program in video game history. Despite reaching a larger audience than any computer game to come before it, however, it still ultimately remained confined to university computer labs and entertained a relatively small portion of the U.S. population. As Russell told Kent, the hackers briefly toyed with the idea of making money on the game, but in 1962 it was still not possible to create a system cheap enough to qualify as a consumer product. It would require nearly another decade of innovation in computer technology and solid-state components before a commercial video game could finally become a reality.

Before World War II, MIT had not been much of a digital computer hotspot. While Howard Aiken at neighboring Harvard and John Atanasoff at Iowa State College were exploring digital solutions to solving complex differential equations, MIT remained firmly planted in the analog world with Vannevar Bush’s differential analyzer. During the war, however, the university became one of the primary centers for war-related scientific research. From the development of fire control systems at the Servomechanisms Laboratory to the breakthroughs in radar delivered by the Radiation Laboratory, MIT secured its place in the military-industrial complex as a critical research hub and became deeply involved in digital computer design through Projects Whirlwind and SAGE.

As Project Whirlwind gathered steam in 1950, MIT provost Julius Stratton formed a committee chaired by physics professor Philip Morse to study the question of whether and how MIT should introduce a computer for general use by faculty and staff at the university. In 1954, the committee returned a recommendation that MIT should build a Computation Center on campus “to aid faculty in keeping up to date on computer use within their fields and to assist them in introducing the use of computers into their courses; to educate all MIT students in computer use; and to explore and develop new ways of using computers in engineering and scientific research.” (Source: Guide to the Records of the Massachusetts Institute of Technology Computation Center) After considering whether to re-purpose the Whirlwind I or invest in a commercial machine, Morse decided in July 1955 to recommend MIT acquire an IBM 704 computer — which he managed to convince the company to provide free of charge, but would not be ready until 1957. Formally announced on September 23, 1955, the Computation Center was incorporated into the forthcoming Building 26 as an 18,000 square foot area near the northwest corner of the building dedicated solely to housing the 704 computer. (Source: A Century of Electrical Engineering and Computer Science at MIT, 1882-1982 by Karl Wildes and Nilo Lindgren) The center came online with the installation of the 704 in 1957 just as a new generation of college students that had received limited exposure to computers in the mid-1950s matriculated to MIT bound and determined to learn everything they could about the new machines. The interaction of these students with MIT’s new computing resources ultimately resulted in the creation of the first widely disseminated computer game.

The Tech Model Railroad Club

Alan Kotok (seated right with glasses), TMRC member and early computer hacker

In September 1946, a group of 26 students (according to the membership rolls maintained by TMRC on its website) established a new organization on the MIT campus called the Tech Model Railroad Club (TMRC). Located in Building 20, which had been built during World War II to house the Radiation Laboratory, TMRC dedicated itself to building and operating what quickly became an immense model railroad system. As discussed in Stephen Levy’s book Hackers: Heroes of the Computer Revolution, this work attracted two distinct types of students: the train and modelling buffs that would meticulously construct accurate railroad cars and elaborate scenery, and the electrical engineering buffs of the Signals and Power (S&P) Subcommittee that would constantly update and refine a track control system of impressive complexity described by Levy as appearing like “a collaboration between Rube Goldberg and Wernher von Braun.” Spending long hours together under the train layout installing parts donated by Western Electric or scrounged from Eli Heffreon’s junkyard in nearby Somerville, members of the S&P quickly bonded over shared interests and even developed their own lexicon. For example, a person who studied instead of joining in the fun was called a “tool,” garbage was called “cruft,” and a clever project undertaken just for the fun of it was called a “hack.” Ultimately, this group of tinkerers would launch the computer revolution referenced in the title of Levy’s book.

Hackers paints portraits of the key TMRC members that matriculated to MIT in 1958. Foremost among them were Alan Kotok and Peter Samson. According to Levy, Kotok grew up in the New Jersey suburbs of Philadelphia, where his parents learned he was an electrical engineering prodigy when he was already building and wiring lamps by the time he was six years old. As touched on in Hackers and elaborated on in an oral history Kotok conducted with the Computer History Museum, Kotok’s first exposure to a computer was a high school field trip to a Socony-Mobil research laboratory in Paulsboro, NJ (Note: Hackers claims the facility was in nearby Haddonfield, but Kotok’s contention in his oral history that it was in Paulsboro appears to accurate), where the students not only viewed a mainframe computer, but actually ran through a programming exercise using punched cards. From that day forward, Kotok knew his future lay with computers, which is why he applied to MIT. Interested in model railroads, Kotok quickly gravitated to TMRC, where according to Levy he was quickly accounted one of the best electrical engineers in S&P.

Samson, on the other hand, was a local boy who grew up just thirty miles away from the university in Lowell, Massachusetts. His first exposure to computers was a television program on the Boston public TV channel WGBH that gave a basic introduction to computer programming. Inspired, he learned everything he could about computing and actually tried to build his own computer using relays pried out of pinball machines. He also viewed computers on trips to MIT, where he resolved to continue his education after high school. Samson joined TMRC on the first day of Freshman orientation in Fall 1958 and was instantly hooked when he beheld the complex system of wires, relays, and switches that kept the track running. TMRC members received their own key to the club room after putting in forty hours on the layout: Samson earned his key in less than three days.

From available evidence, it appears few TMRC upperclassmen shared the same interest in computers as the class of 1962. One that did was Bob Saunders, who joined TMRC in 1956 and by 1958 had become the president of the S&P Subcommittee. Unlike Kotok and Samson, Saunders appears not to have received exposure to computers before matriculating to the school. Levy does describe several engineering exploits he undertook as a boy in the suburbs of Chicago, however, including the construction of a six-foot-tall high-frequency transformer that Saunders claimed blew out television reception for miles around and working a summer job at the phone company installing central office equipment. Indeed, it was the telephone parts used in the train control system that first attracted Saunders to TMRC.

Samson, Kotok, and several other TMRC students gained exposure to the IBM 704 in the Computation Center in Spring 1959 through the first computer course MIT had ever offered to Freshmen, and Kotok even became intimately involved in a chess project being implemented on the computer (and which will be discussed in detail in a later post), but Levy recounts that this experience did not satisfy the bright and curious TMRC members. As a batch processing computer, the 704 required trained IBM staff to actually run programs and provided little feedback to the students and professors who would bring their punched cards to Building 26 and return hours later to see the results, all the while hoping no serious errors had prevented the program from running. Levy, echoing the words of Ted Nelson in his seminal 1974 work Computer Lib, compared these interactions to acolytes (the programmers) asking for divine aid from a fickle god (the computer) through a dedicated priesthood (the operators). This metaphor of a computer priesthood remains an oft-invoked image to this day when discussing batch processing mainframes. Frustrated by their limited access to the 704, TMRC students searched for alternative means to scratch their computing itch.

As described by Levy, Peter Samson particularly enjoyed stalking the hallways of Building 26 at all hours looking for new activities to feed his insatiable curiosity. He would trace wiring, examine telephone switching equipment, and look for unguarded technology to fiddle with. One of these excursions led him to the Electronic Accounting Machinery (EAM) room in the basement, where the university had installed several IBM accounting machines, including an IBM 407. These were electromechanical tabulators of limited capability, but they could read and sort cards and print out the results. Even better, they were only guarded during the day, making the 407 the closest thing to a computer to which TMRC members could secure direct access. Before long, Samson and other TMRC members could be found clustered around the 407 late into the night using the machine to keep track of the expanding array of switches under their train layout and seeing just how far they could push the technology. This work on the 407 represented one of the earliest manifestations of a new computer-centric culture within TMRC.

Hacking the TX-0

Jack Dennis, the former TMRC member and MIT professor that introduced TMRC to the Tx-0

In July 1958, Lincoln Laboratory decided it had no further need for the TX-0 computer built by Ken Olsen and Wes Clark and therefore placed it on semi-permanent loan to MIT, which housed it in the Research Laboratory of Electronics (RLE) in Building 26, located, according to Levy, just one floor above the 704 in the Computation Center. As the computer was coming online, a new MIT instructor by the name of Jack Dennis was just settling into his office down the hall. An MIT alum, Dennis, according to a TX-0 retrospective in the Spring 1984 issue of the Computer Museum Report, had recently completed his dissertation and accepted the instructor position in the fall of 1958, but he was uninterested in pursuing his dissertation topic further. Dennis was soon drawn to the nearby TX-0 and began writing programs for the computer, the most important of which were FLIT, a debugger he wrote with Thomas Stockham, and MACRO, an assembler. These programs allowed a programmer to work in assembly language rather than the more difficult machine language and more easily identify and correct bad code, therefore opening TX-0 programming to a larger user base. About a year and a half after the TX-0 arrived, Dennis was placed in charge of the machine.

Unlike the 704 in the Computation Center, which was operated by trained staff, the TX-0 was generally available for faculty and graduate student research: all a person needed to do was sign up for a block of time. Jack Dennis, however, wanted to go a step further. As an undergraduate, Dennis had the opportunity to program on the Whirlwind, and he believed that interested undergraduate students were a valuable resource that should be encouraged to run their own computer experiments. Dennis had also joined TMRC as a freshman in 1949 and still had contacts within the group, so he knew exactly where to go to recruit his cadre of interested programmers. In his oral history, Alan Kotok remembers Dennis approaching TMRC members in Fall 1958 and asking if they would like to learn to program the TX-0. He took aside an interested group of students that included S&P president Bob Saunders and freshmen Kotok, Samson, Dick Wagner, and Dave Gross and delivered a crash course on the TX-0. The students were amazed to discover a computer that allowed them to program directly and fix their code on the fly. With Dennis’s support, they negotiated with the people in charge of the computer, Earl Pugh and John McKenzie, who agreed to allow them access to the computer during blocks of time not already committed to official research.

During the day, the TX-0 was usually being put to serious use, but few projects were ever run overnight. Therefore, the TMRC members became nocturnal creatures, ignoring both their classes and any semblance of a social life to maximize the amount of time they could spend programming the machine. The young coders derived great joy from pushing the computer to its limits and mastering its capabilities. Like the work they did on the railroad in building 20, the projects they undertook on the TX-0 purely for the fun and the challenge came to be called “hacks,” and the programmers began referring to themselves as “hackers.”

Few of the programs created by the TMRC coders did anything useful — or at least nothing useful enough to justify employing a multi-million dollar computer. Hackers and the Computer Museum Report describe several of these programs.Peter Samson created a program to convert Arabic numbers to Roman numerals and then puzzled out a way to manipulate the primitive built-in audio speaker to play simple, single-voice melodies using a square wave. Kotok discovered a way to interface an FM receiver with the analog-to-digital converter on the computer to create a program he called the Expensive Tape Recorder, while Wagner, who had been using an electro-mechanical calculator in a numerical analysis class, was inspired to write a program called Expensive Desk Calculator.

The Demo Scene

A screenshot of an emulated recreation of MOUSE

In addition to the experiments of the TMRC hackers, the TX-0 also became home to a number of demos. As explained by J.M. Gratez in his August 1981 article for Creative Computing, “The Origin of Spacewar,” getting the general public interested in early computers was rarely easy. While many people were attracted by the high technology on display, they were soon bored watching a computer work, as there were no manifestations of its activity save for blinking lights and whirring tape. This quickly led programmers to create programs that were visually striking and/or interactive in order to generate interest in computer use. The previously discussed Bertie, NIMROD, MIDSAC pool, and Tennis for Two were all essentially interactive demos created for this purpose, and TX-0 programmers were soon crafting their own demos to achieve the same result.

The TX-0 demo programmers most likely took some inspiration from the program recognized as the earliest computer demo, a bouncing ball program created on the Whirlwind I by Charles Adams in 1950. As described by Graetz, this simple program began with a single dot falling from the top of the screen and bouncing when it hit the bottom of the screen, accompanied by a sound from the Whirlwind speaker. The ball would continue to bounce around all four sides of the screen until finally running out of momentum and rolling off through a hole in the floor. While the program was simple, the effect proved stunning in a time when no other computer could actually update a CRT display in real-time.

Graetz describes several demos on the TX-0. One, called HAX, would generate an ever-changing array of shapes to show off the capabilities of the TX-0’s CRT. Another was a Tic-Tac-Toe game — played against the computer by typing commands using the flexowriter — designed to show off the computer’s interactivity. Perhaps the most impressive hack, combining the visual interest of HAX and the interactivity of Tic-Tac-Toe, was the MOUSEprogram developed by Doug Ross and John Ward and first publicized in January 1959. As described in the Spring 1984 Computer Museum Report, Ward had observed people programming on the Whirlwind at Lincoln Labs but had never had the opportunity to program the machine himself. Therefore, when the TX-0 became available, he decided to sign up for time but did not know what type of program to write. Remembering a program he had developed while working with a UNIVAC 1103 on Eglin Air Force Base with Ross, the head of MIT’s Computer Applications Group and the person who first coined the term “computer-aided design” (CAD), Ward convinced Ross to help him create a similar program on the TX-0. In the finished product, with logic by Ross and a display by Ward, the user would create a maze directly on the CRT by erasing lines from an 8×8 grid of squares using the light pen and then place pieces of cheese throughout the maze. A mouse would then traverse the maze while eating all the cheese. The mouse would run out of energy if it did not reach a piece of cheese within a certain amount of time, but it would remember the paths taken in each attempt and therefore develop a more efficient route over time. A variant replaced the cheese with martini glasses and had the mouse stagger the more it drank.

MOUSE and Tic-Tac-Toe highlighted the potential of an interactive computer as a device for playing games, but the TX-0 display remained too limited to create a truly engaging interactive visual experience. In 1961, however, DEC donated one of the first PDP-1 computers to MIT, which was placed in the RLE in the room next to the TX-0. Sporting a more sophisticated display than the TX-0, the PDP-1 was the perfect platform for the TMRC hackers to take the lessons learned through programming the TX-0 to create the first truly influential computer game, Spacewar!